1. Field of the Invention
The invention relates to a method for printing or marking wires with identification indicia as part of a wire harness production process and while the wires are connected with connectors. The invention also relates to apparatus printing identification indicia on wires.
2. Description of the Related Art
Some electrical connectors have a plurality of terminal fittings mounted in a connector housing. Wires are connected to the terminal fittings and extend from the connector housing. The respective wires generally are of different colors to facilitate individual identification. This method of identifying wires increases the number of different types of wires required, and therefore decreases productivity and increases costs. As a result, some connectors employ several wires of the same color and print the wires with identifying characters and/or marks.
The identifying indicia typically are applied to the wires during a wire measuring operation. The marked wires then are cut and terminals are mounted to wire ends for insertion into a connector housing. However, the wire measuring operation must be stopped every time printing is applied to the wire. As a result, production efficiency and output are reduced. Furthermore, the terminal is mounted on the wire and inserted into the connector housing after printing. Consequently, the position and direction of printing on the wire drawn from the connector may be displaced. The position and orientation of the printing may be specified beforehand. However, such displacements need to be checked and corrected during the assembly process, and hence production efficiency is reduced further.
An object of the present invention is to solve the above problems and to improve the productivity of a wiring harness.
The invention is directed to a wire printing method, comprising a step of providing at least one wire that is connected with a connector and then feeding the wire to a marking section together with the connector. The feeding step preferably is carried out with the connector and/or the wire at least partly supported by a palette or holder for conveyance. The method then comprises pulling the wire that extends from the connector substantially straight in the marking section and holding the substantially straightened wire in the marking section. The method further comprises applying identifying indicia to the wire in this state by a printing device provided in or near the marking section.
According to a preferred embodiment, the step of applying identifying indicia comprises applying printing to an insulation coating of the wire by a non-contact printing device provided in the marking section.
The printing is applied to the wires after the wires have been connected with the connector. Thus the printing can be done without stopping a wire measuring operation, thereby eliminating a loss of time.
The invention also is directed to a wire printing apparatus that comprises a palette or holder for holding a connector such that the connector can be fed at an angle to the direction that the wire extends from the connector. The angle of feed preferably is substantially a right angle. The apparatus also comprises a wire receiving portion or table on which portions of wires that extend from the connector can be placed. A wire-correcting device is provided, including an elevating or moving mechanism and an advancing mechanism. The apparatus further comprises a holder including an elevating or moving mechanism and a printing or marking device. The printing or marking device is provided substantially above or near a marking section of the apparatus. The wire correcting device can be moved to press the wire fed to the marking section and can be advanced away from the connector for at least partly straightening the wire on the wire receiving portion in the wire drawing direction from the connector. The holder can be moved to hold the substantially straightened wire in the marking section, and printing can be applied to the wire by the printing device in this state. According to a preferred embodiment, the printing device is a non-contact printer.
The wire connected with the connector may be buckled or bent. In this situation, printing cannot be applied directly to the wire because the buckled or bent wire cannot be positioned precisely. Thus, according to the present invention, the wire that extends from the connector is pulled sufficiently to be straightened by the wire-correcting device, and printing is applied while the holder holds the straightened wire in the center of the marking section. With such an arrangement, no omission of printing occurs due to the displacement of the wire. Additionally, the position and orientation of printing can be maintained constantly. Thus, it is not necessary to correct the displacement even when the position and orientation of printing are specified.
Preferably, a plurality of wires extend from a single connector and are fed successively to the marking section by moving the palette in a direction at an angle to the wire, and preferably substantially normal to the wires that extend from the connector.
This apparatus may additionally comprise a moving mechanism for moving the palette that holds the connector in the direction normal to the wires. The moving mechanism may function after the wires that extend from the connector are fed successively to the marking section. Accordingly, printing can be applied continuously.
The wire-correcting device preferably comprises a roller that can be rotated in a wire straightening direction. The roller may be formed with a substantially V-shaped groove, and the roller may be rotated in a wire straightening direction. Thus, the wire can be straightened while being centered by the surface of the groove of the roller.
Alternatively, the wire-correcting device may comprise a roller that has no groove. The roller is rotated in a wire straightening direction and the wire is pushed and centered into a substantially V-shaped groove formed in the wire-receiving portion by the roller to be.
The wire-correcting device may comprise two eccentrically arranged rollers mounted on a holding member having a pivotal center displaced from the centers of rotation of the two rollers. Thus the two wires can be pulled simultaneously to enable simultaneous application of printing to the wires. Additionally, the two wires may have different diameters.
The wire-correcting device preferably comprises a roller, which causes no fretting to prevent the wires from being scratched or otherwise damaged. For example, the wire-correcting device may be provided with a soft pad and may have substantially V-shaped grooves for centering. The wires can also be straightened by a method for pressing the wires by the soft pad while lightly bringing the surfaces of the substantially V-shaped grooves into contact with the wires.
The holder may comprise a chuck for gripping the substantially straightened wire from opposite sides. A brush may be operable with the wire-correcting device to brush gripping surfaces of the chuck by passing the brush between the gripping surfaces during advancing and retracting movements of the wire-correcting device. The brush preferably is used when a laser marker is used as the printing device.
A sensor may be provided for detecting whether the wire is positioned in the marking section. The printing device then applies printing to the wire in accordance with a detection signal from the sensor. Thus, a laser beam is not emitted if no wire is present, and damage to the table by the laser can be avoided.
The holder may comprise at least one pressing element for pressing and holding the substantially straightened wires. The pressing element is formed with a through hole in or through which printing can be applied, and the straightened wire can be pressed and held from above by the holder. This construction is particularly effective when printing is applied simultaneously to a plurality of wires. More particularly, this construction enables the respective wires to be held at simultaneously by one holder unlike the chuck, and is not subject to restriction on installation space.
A laser beam of a laser marker is likely to produce cinders of the insulation coating, and the cinders are likely to adhere to the gripping surfaces of the chuck. However, the brush removes adhered cinders and other such debris from the gripping surfaces before the chuck grips a next wire. Therefore, adhered matter on the gripping surfaces is not transferred to the wire and does not smear the applied identification markings.
These and other objects, features and advantages of the present invention will become apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments may be described separately, single features of the respective embodiments may be combined to additional embodiments.